The AcpiNotifier plugin

The AcpiNotifier plugin handles the email LED found on some laptops.
It makes it possible to see whether you have new emails from the other
side of the room, without even unlocking the screen. The plugin handles
the following types of laptops:

ACER,

ASUS,

IBM,

Fujitsu,

and others

Here are a few screenshots illustrating the features:

The plugin preferences page, showing a warning, because the user
has chosen the wrong ACPI type for his laptop.